Unable to break a three-day slide, shares of Groupon tumbled again on Wednesday, as more investors dumped shares.

For the first time since it went public earlier this month, Groupon broke below its offering price of $20 per share. Shares of Groupon fell 16 percent on Wednesday to close at $16.96.

The popular daily deals site had wrestled with intense scrutiny and volatile equity markets in the weeks leading up to its offering, but its debut was widely heralded as a strong performance. On its first day of trading, Groupon rose as much as 50 percent, before settling at $26.11 per share.

Wednesday’s drop is a disturbing signal for technology investors and other start-ups waiting to go public.

“Selling begets selling,” said Paul Bard, a director of research at Renaissance Capital, an I.P.O. advisory firm. “In the environment we’re in right now, investors are wary of risk, and so these less-seasoned companies will naturally face more selling pressure.”

Technology companies have largely outperformed other sectors in their debuts this year. Shares of LinkedIn, for instance, doubled on their first day of trading, while Yandex, the Russian search engine, surged more than 55 percent on its debut.

But for many, the glitter has come off just as fast. Pandora, which went public in June, has dropped nearly a third from its offering price. Renren, often described as the Facebook of China, is about 74 percent below its offering price. Both Pandora and Renren tumbled again on Wednesday, with Pandora off roughly 11 percent and Renren down 6 percent.

According to data from Renaissance Capital, the technology sector has seen 41 I.P.O.’s this year, with an average first-day pop of 20.3 percent. Year-to-date, however, the group has lost about 13.1 percent in value.

The widespread pullback seems to suggest that investors, while eager to capitalize on first-day gains, do not have the confidence, or stomach, to hold on to the Web’s latest offerings. That apprehension is likely to be a major concern for high profile start-ups, like Zynga and Facebook, both of which are expected to go public in the coming months.

“When returns turn negative, that creates a problem for the I.P.O. market,” Mr. Bard said. “Because what’s the incentive to buy into the next I.P.O.? Bankers are now probably revisiting how many and which deals they will launch.”